Validation and extension of the SUCCESS score for Fuchs dystrophy after cataract surgery

Accurate preoperative identification of patients with Fuchs endothelial corneal dystrophy (FECD) who are at risk of requiring endothelial keratoplasty (EK) after cataract surgery remains challenging. The SUbClinical Corneal Edema Scheimpflug Study (SUCCESS) score was previously developed to estimate this risk using Scheimpflug tomography. We aimed to prospectively and externally validate the SUCCESS score in an independent multicenter cohort and determine whether the incorporation of corneal densitometry improves predictive performance and clinical utility.

In this prospective multicenter cohort study, 207 eyes from 177 patients with FECD grade ≥ 2 and visually significant cataract were enrolled across six tertiary hospitals in Spain (June 2020 to October 2024), with follow-up through May 2025. After predefined exclusions, 178 eyes (149 patients) were analyzed. The original SUCCESS score was used without recalibration. An extended model incorporated peak mean corneal densitometry within the central 3-mm zone. Time-to-event analyses were performed using Cox proportional hazards models. Discrimination, calibration, reclassification, and clinical utility were assessed using Harrell's C-index, Brier score, net reclassification index (NRI), integrated discrimination improvement (IDI), and decision curve analysis.

Over a median follow-up of 37.0 months (interquartile range [IQR], 10.1-45.9), 38 eyes (21%) met the criteria for EK, with 82% of events occurring within 6 months after phacoemulsification. The original SUCCESS score demonstrated good discrimination (C-index = 0.80; 95% confidence interval [CI], 0.73-0.86) with slight underestimation of absolute risk (predicted 16.4% vs. observed 21.6%). Incorporation of corneal densitometry improved discrimination (C-index = 0.85; 95% CI, 0.79-0.90; ΔC = + 0.05; P = 0.0047), reduced prediction error (ΔBrier = - 0.019; P < 0.001), and enhanced risk reclassification (NRI = 0.39; 95% CI, 0.14-0.64; P = 0.002), including correct upward reclassification of 26% of eyes requiring EK. The extended model provided greater net benefit at relevant decision thresholds (25%-50%).

In this multicenter external validation study, the SUCCESS score demonstrated a robust performance in predicting postoperative EK in FECD. The addition of corneal densitometry provided incremental improvements in discrimination and clinically meaningful risk stratification, particularly in intermediate-risk cases. Standardized Scheimpflug-based risk assessment may support individualized surgical planning and referral decisions.